Pochoir (pronounced "PO-shwar") is a compiler and run-time system for implementing stencil computations on multicore processors. A stencil defines the value of a grid point in a d-dimensional spatial grid at time t as a function of neighboring grid points at recent times before t. A stencil computation computes the stencil for each grid point over many time steps.

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Pochoir (pronounced "PO-shwar") is a compiler and runtime system for implementing stencil computations on multicore processors. A stencil defines the value of a grid point in a ''d''-dimensional spatial grid at time ''t'' as a function of neighboring grid points at recent times before ''t''. A stencil computation computes the stencil for each grid point over many time steps. Using Pochoir, a user specifies a computing kernel and boundary conditions using a simple stencil language embedded in C++. The Pochoir compiler produces cache-efficient multithreaded C++ code that can be compiled with the Intel 12.0 compiler for C++ with the Cilk multithreading extensions, which is available as part of the [http://software.intel.com/en-us/articles/intel-parallel-composer/ Intel Parallel Computer] suite. The Pochoir package contains two main components: a C++ template library for debugging and testing Pochoir compliance and a domain-specific compiler written in Haskell that produces highly optimized code. (Currently, the Pochoir package has only been tested on Linux systems.)

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In Pochoir, user typically just need to specify his /or her stencil computing kernel and boundary conditions in an embedded domain specific language in C++. Depending on the purpose of checking functional correctness or performance, user can employ either a native C++ compiler or Pochoir compiler to compile and run his /or her code. If the user employs the Pochoir compiler, the basic parallelization and optimization strategy of Pochoir is divide-and-conquer (cache-oblivious algorithm). In higher dimensional space-time grid, Pochoir employs a novel cutting strategy of simultaneous space cut.

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Here is an example of a 2D heat equation coded in Pochoir:

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<nowiki>

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#define mod(r,m) ((r)%(m) + ((r)<0)? (m):0)

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Pochoir_Boundary_2D(heat_bv, a, t, x, y)

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return a.get(t,mod(x,a.size(1)),mod(y,a.size(0)));

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Pochoir_Boundary_End

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Pochoir is an open source software project hosted by SuperTech group at CSAIL, MIT. You are invited to contribute in many forms (documentation, translation, writing code, fixing bugs, porting to other platforms...).

The Pochoir package contains three (3) main components: an embedded domain specific language (EDSL) in native C++ for stencil, a C++ template library for baseline run, and a domain specific compiler in Haskell for optimal run.

Comparing the number of grid points processed per second (semilogarithmic scale) for Pochoir-generated code on 12 cores versus serial- and parallel-loop implementations. In all figures, the top curve is for the Pochoir-generated code, the middle curve is for parallel loops, and the bottom curve is for serial loops. (a) A 3D wave equation with a non-periodic boundary condition executing for 1000 time steps. (b) A 2D heat equation on a torus executing for 3200 time steps. (c) 1D pairwise sequence alignment (no time step). (d) A Lattice Boltzmann method with a non-periodic boundary condition for 3000 time steps.

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for (int x = 0; x < X; ++x)

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for (int y = 0; y < Y; ++y)

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cout << u(T, x, y);

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return 0;

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}</nowiki>

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Pochoir is an open-source software project hosted by Supertech group at CSAIL, MIT. You are invited to contribute in any form (documentation, translation, writing code, fixing bugs, porting to other platforms, etc.). We are particularly interested in developing a set of real-world example stencil computations.

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== <br>Performance Graphs ==

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[[File:hotParSubmission1.png|700px]]

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Comparing the number of grid points processed per second (semilogarithmic scale) for Pochoir-generated code on 12 cores versus serial- and parallel-loop implementations. In all figures, the top curve is for the Pochoir-generated code, the middle curve is for parallel loops, and the bottom curve is for serial loops. (a) A 3D wave equation with a nonperiodic boundary condition executing for 1000 time steps. (b) A 2D heat equation on a torus executing for 3200 time steps. (c) 1D pairwise sequence alignment (no time step). (d) A Lattice Boltzmann method with a nonperiodic boundary condition for 3000 time steps.

== <br>Pochoir Team ==

== <br>Pochoir Team ==

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The project is jointly developed by [https://groups.csail.mit.edu/sct/wiki/index.php?title=Main_Page SuperTech group at MIT] and [http://www.intel.com/?en_US_01 Intel Corp].. The core team includes:

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The Pochoir project is joint research by the [https://groups.csail.mit.edu/sct/wiki/index.php?title=Main_Page Supertech Research Group at MIT], [http://www.intel.com/?en_US_01 Intel Corporation], [http://www.cs.sunysb.edu/ Department of Computer Science, State University of New York at Stony Brook], [http://math.mit.edu/~stevenj/group.html Nanostructures and Computation Group at MIT], and [http://www.fudan.edu.cn Fudan University in China]. The core team includes the following researchers:

Please send your name and affiliation to [mailto:pochoir@csail.mit.edu Pochoir Development List] to let us know that you are interested in using Pochoir, so that we can provide better technical support to all our known customers, which includes bug fix, new release notification, new feature incorporation, etc.

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'''Pochoir''' is covered by the [http://www.gnu.org/licenses/gpl.html GNU Public License version 3.0]

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'''Pochoir''' is released under the [http://www.gnu.org/licenses/gpl.html GNU Public License version 3.0].

Latest revision as of 21:36, 28 August 2012

Contents

Welcome to Pochoir

The Pochoir Stencil Compiler

Pochoir (pronounced "PO-shwar") is a compiler and runtime system for implementing stencil computations on multicore processors. A stencil defines the value of a grid point in a d-dimensional spatial grid at time t as a function of neighboring grid points at recent times before t. A stencil computation computes the stencil for each grid point over many time steps. Using Pochoir, a user specifies a computing kernel and boundary conditions using a simple stencil language embedded in C++. The Pochoir compiler produces cache-efficient multithreaded C++ code that can be compiled with the Intel 12.0 compiler for C++ with the Cilk multithreading extensions, which is available as part of the Intel Parallel Computer suite. The Pochoir package contains two main components: a C++ template library for debugging and testing Pochoir compliance and a domain-specific compiler written in Haskell that produces highly optimized code. (Currently, the Pochoir package has only been tested on Linux systems.)

Pochoir is an open-source software project hosted by Supertech group at CSAIL, MIT. You are invited to contribute in any form (documentation, translation, writing code, fixing bugs, porting to other platforms, etc.). We are particularly interested in developing a set of real-world example stencil computations.

Performance Graphs

Comparing the number of grid points processed per second (semilogarithmic scale) for Pochoir-generated code on 12 cores versus serial- and parallel-loop implementations. In all figures, the top curve is for the Pochoir-generated code, the middle curve is for parallel loops, and the bottom curve is for serial loops. (a) A 3D wave equation with a nonperiodic boundary condition executing for 1000 time steps. (b) A 2D heat equation on a torus executing for 3200 time steps. (c) 1D pairwise sequence alignment (no time step). (d) A Lattice Boltzmann method with a nonperiodic boundary condition for 3000 time steps.

Current Release

Please send your name and affiliation to Pochoir Development List to let us know that you are interested in using Pochoir, so that we can provide better technical support to all our known customers, which includes bug fix, new release notification, new feature incorporation, etc.